Compatibility Study of Ethylene Propylene Diene Monomer Rubber with Polyisobutylene for Cable Terminals

Material compatibility in cable terminals is essential to ensure the insulation performance of electrical insulation systems. In this study, the compatibility between ethylene propylene diene monomer (EPDM) rubber as a cable terminal stress cone material and polyisobutylene as an insulating filler was investigated. By analyzing the morphology, swelling properties, and mechanical properties of the EPDM rubber before and after performing a compatibility test, in combination with Fourier transform infrared spectroscopy and thermogravimetric analyses, the mechanism of the interaction between the EPDM rubber and polyisobutylene was investigated. In addition, the physicochemical and electrical property changes of polyisobutylene were evaluated. The results showed that the EPDM rubber was incompatible with polyisobutylene. Due to their similar molecular structure, polyisobutylene continuously diffused into the three-dimensional network of the EPDM rubber during the compatibility test, resulting in the relaxation of the molecular chains of the EPDM rubber and, in turn, the weakening of the intermolecular force. As a result, the volume of the EPDM rubber expanded, the mass increased, and the mechanical properties were seriously degraded, as were the physicochemical and electrical properties of the polyisobutylene impregnating the EPDM rubber.